PTEN and glioblastoma: Our data also showed that, although the long-term tumorigenic GBM cultures used in this study displayed loss of heterozygosis (LOH) at specific loci on chromosome 10q (i.e., PTEN and RET), they contained 2 copies (PT2, PT3, PT5, PT6) or 3 copies (PT1, PT4) of chromosome 10, independently from the in vivo invasion behavior.